Fluorescent lamp control



Sept. 15, 1970 c. W B 3,529,207

FLUORESCENT LAMP CONTROL Fiied April 18, 1968 F]. E I INVENTOR. i PHILIPC. WEBB ATTORNEY United States Patent O" 3,529,207 FLUORESCENT LAMPCONTROL Philip C. Webb,.4752 Pin Oak Trail,

Jackson, Mich. 49201 Filed Apr. 18, 1968, Ser. No. 722,440 Int. Cl. Hb39/00 US. Cl. 315-94 6 Claims ABSTRACT OF THE DISCLOSURE OUTLINE OFINVENTION The transistor is substituted for the usual current limitingballast of fluorescent lights. A biasing connection to a controlterminal of the transistor automatically regulates the transistor topass the necessary high starting voltage to the lamp, and reduce theoperating current and voltage in the lamp, when the internal resistanceof the lamp is reduced as the lamp starts. The biasing connection to thetransistor includes a resistor, which may be variable and used as abrightness control for the lamp, and a secondary coil of the powersupply transformer of the lamp.

Unexpectedly, the transistor is conducting on both cycles of alternatingcurrent applied to the transistor and its biasing connection, sooppositely connected transistors are not required to providesubstantially continuous energization of the lamp.

The drawings, of which there is one sheet show a preferred form of thecontrol circuit connected to a fluorescent lamp.

FIG. 1 is a schematic wiring diagram of the connections to a fluorescentlamp with the control elements of the invention connected thereto.

FIG. 2 is a diagrammatic view showing the wave form of the currentflowing through the lamp during operation.

The diagram shows the tubular envelope 1 of a fluorescent lamp withfilaments 2 and 3 in its ends. An alternating current source indicatedat 4 is selectively connectable by the switch 5 to the primary 6 of atransformer indicated generally at 7. One secondary winding 8 of thetransformer is connected to one side of the power source and to filament2. Another secondary winding 9 is connected to the other filament 3 andis connected through a transistor 10 to the opposite side of the powersource through conductors 11 and 12.

The conductor 11 connects between the emitter 13 of the transistor andthe opposite end of the primary winding 6. The conductor 12 connectsbetween the collector 14 of the transistor and one side of the winding 9and the filament 3. Together, the conductors 11 and 12 constitute aregulating conductor for filaments 3 and the lamp.

The base 15 of the transistor is connected by the conductor 16 to aresistor 17, which may be variable. The resistor is connected byconductor 18 in series with a third coil 19, which is connected toconductor 11 and the power source.

In operation of the lamp and its control, closing of the 3,529,207Patented Sept. 15 1970 switch 5 provides heater current to the filament2 at the alternating potential of one side of the power source. Theother filament 3 is supplied with an approximately equal heating currentby the winding 9. However, the potential of the filament 3 relative tothe filament 2 is determined by the action of the transistor 10 and itscontrol base 15. Generally, the absolute potential of filament 3 willapproximate the alternating potential of the opposite side of the powersource from filament 2; so that an operative potential is createdbetween the filaments 2 and 3 considered as opposite electrodes of thelamp 1. The alternating potential of the side of the power sourceconnected to switch 5 acts, in conjunction with current flow throughconductors 11 and 12, to modulate and integrate the potentials andcurrents transmitted by the transistor, so that the resultant currentthrough the lamp varies as is I CC indicated graphically in FIG. 2. Thecurrent through the lamp 1 does not vary in the same sinusoidal manneras the ordinary commercial alternating current such as is applied 0 theprimary winding 6. Neither does the transistor act as a half waverectifier to create intermittent voltage and current between thefilaments. Instead, the current through the lamp 1 varies as shown bythe graph in FIG. 2.

Considering the cycle of ordinary sixty cycle commercial current to beindicated by the lines 20 in FIG. 2, the

' resultant current in the lamp 1 rises from zero at 21 to anintermediate peak 22, followed by a small fluctuation 23. Following thefluctuation, the lamp current rises to a sharp and higher peak orpositive value at 24. The current then falls rapidly to a second low,but still positive fluctuation, indicated by the dip 25. From this pointthe current decreases through zero to a negative peak 26. The cycle iscompleted by a rise (decrease of negative value) to the zero startingvalue. This cycle of current maintains practically constant transmissionor emission between the filaments 2 and 3, and at the standard of sixtycycle commercial current provides illumination without noticeableflicker.

The following specific values or factors in the circuit provide aninstallation of a currently standard 40 watt F-40 type of fluorescentlamp in a 240 volt supply line. The windings 8 and 9 provide a heatervoltage to the filaments 2 and 3 of 6.3 volts, which is somewhat higherthan the 5 volts recommended for F-40 type lamps.

The resistor 17. if variable, will start and operate the lamp at 10,000ohms, with a resultant brightening of the lamp. A fixed 8,000 ohm, 10watt resistor starts and operates the lamp satisfactory, but with thedevelopment of considerable heat or lost energy in the resistor. Thetransistor may be of the type identified by the designation DTS-423.Winding 19 provides a biasing voltage of 6.3 volts to the base 15through conductors 18 and 16 to the transistor. The third winding 19, inconjunction with resistor 17 provides a control voltage of about 7 voltsbe tween the base 15 and the emitter 13 of the transmitter.

- What is claimed as new is:

1. A control for a fluorescent lamp having spaced filaments comprising,

a transformer having a primary winding adapted to be connected to asource of alternating current,

a first secondary winding in said transformer connected to one side ofsaid primary winding and having terminals adapted to be connected to theends of a first of said filaments,

a second secondary winding in said transformer having terminals adaptedto be connected to the ends of the other of said filaments,

a transistor having base, emitter and collector terminals,

a regulating conductor connecting said second second- 3 ary winding tothe opposite side of said primary winding from said first secondarywinding,

said regulating conductor having two sections connected in seriesthrough said emitter and said co1lector terminals of said transistor,

and a control circuit including a resistor connected bebetween the baseof said transistor and the other side of said primary winding from saidfirst secondary winding,

said control circuit extending through a secondary winding of saidtransformer.

2. A control as defined in claim 1 in which said resistor is variable.

3. A control as defined in claim 2 in which said variable resistor hasboth minimum and maximum resistances of finite values.

4. A control as defined in claim 1 in which said second secondarywinding is connected to said regulating conductor between a terminalconnection to said other of said filaments and said transistor.

7 4 Y e .0 5. A control as defined in claim 4 in which there is a thirdsecondary winding in said transformer,

said third winding being connected in series with said resistor in saidcontrol circuit. 6. A control as defined in claim 5 in which saidsecondary windings supply voltages between 5 and 7 volts, and in whichsaid resistor is variable between 5,000 and 10,000 ohms.

References Cited UNITED STATES PATENTS 3/1969 Miller et al. 315-94 US.Cl. X.R.

